Method and apparatus for transmitting and receiving feedback information for inter-cell cooperative transmission in wireless communication cellular system

ABSTRACT

A method for transmitting feedback information for collaborative transmission in a cellular radio communication system is provided. The method includes receiving, from the base station, collaborative cell information indicating a plurality of collaborative cells, determining at least two preferred collaborative cells among the plurality of collaborative cells, generating feedback information including cell indicators for discriminating between the at least two preferred collaborative cells and the other cell, precoding matrix indicators for the at least two preferred collaborative cells, and channel quality indicators, and transmitting the feedback information via one of a control channel and a data channel.

This application is a continuation application of a prior applicationSer. No. 13/376,253, filed on Dec. 5, 2011, which claims the benefitunder 35 U.S.C. §371 of PCT/KR2010/003592, filed on Jun. 4, 2010, whichclaims the benefit of a Korean patent application filed on Jun. 4, 2009in the Korean Intellectual Property Office and assigned Serial number10-2009-0049557, the entire disclosure of each of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a feedback informationtransmission/reception method for inter-cell cooperative transmission ina cellular radio communication system and, in particular, to a feedbackinformation transmission/reception method and apparatus in considerationof multiple base stations involved in inter-cell cooperativetransmission.

2. Description of the Related Art

The mobile communication system has evolved into a high-speed,high-quality wireless packet data communication system to provide dataservices and multimedia services beyond the early voice-orientedservices. Recently, various mobile communication standards, such as HighSpeed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access(HSUPA), both defined in 3^(rd) Generation Partnership Project (3GPP),High Rate Packet Data (HRPD) defined in 3^(rd) Generation PartnershipProject-2 (3GPP2), and 802.16 defined in IEEE, have been developed tosupport the high-speed, high-quality wireless packet data communicationservices.

Such recent mobile communication systems adopt Adaptive Modulation andCoding (AMC) and channel sensitive techniques to improve transmissionefficiency. With AMC, the transmitter can control the data amountaccording to channel state. That is, when the channel state is bad, thedata rate is decreased to math a predetermined error rate, and when thechannel state is good, the data transmission rate is increased to matchanother predetermined error rate. In this way, the mobile communicationsystem can transmit large amount of information efficiently. With thechannel sensitive scheduling resource management method, the transmittercan serve the user having superior channel state first selectively amongmultiple users and thus increase system throughput as compared to thegeneral channel allocation and serving method. For example, theclosed-loop precoding, the AMC, and channel sensitive scheduling are thetechniques for using the best modulation and coding scheme at the mostefficient timing based on the partial channel state information fed backby the receiver.

There has been many researches done to adopt Orthogonal FrequencyDivision Multiple Access (OFDMA) to next generation communicationsystems in place of Code Division Multiple Access (CDMA) that has beenused in 2^(nd) and 3^(rd) Generation mobile communication systems. Thestandardization organizations such as 3GPP, 3GPP2, and IEEE aredeveloping standards for enhanced system based on the OFDMA or modifiedOFDMA. It is known that OFDMA promises to increase system capacity ascompared to CDMA. One of the factors affecting the increase of systemcapacity in an OFDMA system is the use of frequency domain scheduling.As the channel sensitive scheduling technique uses the time-varyingchannel for capacity gain, it is possible to increase the capacity gainwith frequency-varying channel characteristic.

The closed-loop precoding, AMC, and channel-sensitive scheduling are thetechniques that are capable of improving the transmission efficiency inthe state where the transmitter has acquired information enough on thetransmit channel. In FDD (Frequency Division Duplex) mode where thetransmitter cannot estimate the state of the transmit channel based onthe receive channel, it is designed for the receiver to report theinformation on the transmit channel to the transmitter. In the mobilecommunication environment, however, the channel state is time-varyingsuch that efficiencies of the closed-loop precoding, AMC, channelsensitive scheduling techniques are degraded.

The cellular radio communication system is designed such that each basestation serves the users within its coverage and hands over the controlon the user getting out of the coverage to another base station. In sucha cellular structure, the user located at the boundary of a cellexperiences interference of the signal transmitted by other basestations such that the channel state is deteriorated. Accordingly, theuser close to the base station is served at a high data rate while theuser located at the cell boundary is served at a low data rage. In orderto solve this problem, it is expected that the 4^(th) generation mobilecommunication system under discussion adopt the collaborativetransmission technique in which multiple base stations transmit signalsto the user located at the cell boundary.

Such a cell involved in the collaborative transmission is referred to ascollaborative cell. The collaborative transmission can be categorizedinto one of a low level collaborative transmission in which thecollaborative cells perform coordinated scheduling or interferenceavoidance beamforming to suppress the interference from neighbor cellsand a high level collaborative transmission in which the collaborativecells transmit the same signals. The low level collaborativetransmission technique makes the scheduling and beamforming decisioncollaboratively with sharing the real transmission signals. Whereas, thehigh level collaborative transmission technique allows the collaborativecells to share even the real transmission signals such that the channelstate of the user located at the cell boundary is highly improved due tothe signal reinforcement rather than interference in spite of thetraffic increase in the network.

FIG. 1 is a diagram illustrating a structure of an uplink subframe basedon Single-Carrier Frequency Division Multiple Access (SC-FDMA) in an LTEsystem.

A 10 MHz system bandwidth 103 is composed of total 50 Resource Blocks(hereinafter, referred to as RB). An RB is generated from 12 subcarriersand a basic data transmission scheduling unit. An uplink subframe 101 iscomposed of 14 SC-FDMA symbol durations 105. Physical Uplink ControlChannel (hereinafter, referred to as PUCCH) 106 is transmitted on theRBs at both edges of the system band, and Sounding Reference Signal(hereinafter, referred to as SRS) 109 at the last SC-FDMA symbol 105across the 10 MHz system band 103. Physical Uplink Shared Channel(hereinafter, referred to as PUSCH) 107 is transmitted in the regionwith the exception of the PUSCH and SRS regions of the system band, andReference Signal (hereinafter, referred to as RS) 108 is transmitted onthe SC-FDMA symbol in the middle of each slot 103. PUCCH includesAcknowledge/Negative Acknowledge (ACK/NACK) for Hybrid Automatic RepeatRequest (HARQ) process, Rank Indicator (RI) for downlink datascheduling, Precoding Matrix Indicator (PMI), and Channel QualityIndicator (CQI); and SRS is the signal for user-specific uplink channelstate information acquisition and uplink transmit timing adjustment forthe system bandwidth. RS is the signal carrying the channel statinformation for use in PUCCH and PUSCH demodulation and decoding.

In order to maintain the single carrier characteristics in uplinktransmission, PUCCH and PUSCH are not transmitted in the same subframe.The channel state information can be fed back periodically on PUCCH ornon-periodically on PUSCH allocated for feedback in response to therequest of the base station.

The precoding matrices defined in multi-antenna based LTE system areshown in tables 1 and 2, and the user terminal reports channel stateinformation including the RI and PMI (codebook index or codebookindicator) corresponding to the RI to the base station through PUCCH orPUSCH.

TABLE 1 Codebook Rank index 1 2 0 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\1\end{bmatrix}$ $\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$ 1 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}$ 2 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}$ 3 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- j}\end{bmatrix}$ —

TABLE 2 Codebook Rank Index u_(n) 1 2 3 4 0 u₀ = [1 −1 −1 −1]^(T) W₀^({1}) W₀ ^({14})/{square root over (2)} W₀ ^({124})/{square root over(3)} W₀ ^({1234})/2 1 u₁ = [1 −j 1 j]^(T) W₁ ^({1}) W₁ ^({12})/{squareroot over (2)} W₁ ^({123})/{square root over (3)} W₁ ^({1234})/2 2 u₂ =[1 1 −1 1]^(T) W₂ ^({1}) W₂ ^({12})/{square root over (2)} W₂^({123})/{square root over (3)} W₂ ^({3214})/2 3 u₃ = [1 j 1 −j]^(T) W₃^({1}) W₃ ^({12})/{square root over (2)} W₃ ^({123})/{square root over(3)} W₃ ^({3214})/2 4 u₄ = [1 (−1 − j)/{square root over (2)} −j (1 −j)/{square root over (2)}]^(T) W₄ ^({1}) W₄ ^({14})/{square root over(2)} W₄ ^({124})/{square root over (3)} W₄ ^({1234})/2 5 u₅ = [1 (1 −j)/{square root over (2)} j (−1 − j)/{square root over (2)}]^(T) W₅^({1}) W₅ ^({14})/{square root over (2)} W₅ ^({124})/{square root over(3)} W₅ ^({1234})/2 6 u₆ = [1 (1 + j)/{square root over (2)} − j (−1 +j)/{square root over (2)}]^(T) W₆ ^({1}) W₆ ^({13})/{square root over(2)} W₆ ^({134})/{square root over (3)} W₆ ^({1324})/2 7 u₇ = [1 (−1 +j)/{square root over (2)} j (1 + j)/{square root over (2)}]^(T) W₇^({1}) W₇ ^({13})/{square root over (2)} W₇ ^({134})/{square root over(3)} W₇ ^({1324})/2 8 u₈ = [1 −1 1 1]^(T) W₈ ^({1}) W₈ ^({12})/{squareroot over (2)} W₈ ^({124})/{square root over (3)} W₈ ^({1234})/2 9 u₉ =[1 −j −1 −j]^(T) W₉ ^({1}) W₉ ^({14})/{square root over (2)} W₉^({134})/{square root over (3)} W₉ ^({1234})/2 10 u₁₀ = [1 1 1 −1]^(T)W₁₀ ^({1}) W₁₀ ^({13})/{square root over (2)} W₁₀ ^({123})/{square rootover (3)} W₁₀ ^({1324})/2 11 u₁₁ = [1 j −1 j]^(T) W₁₁ ^({1}) W₁₁^({13})/{square root over (2)} W₁₁ ^({134})/{square root over (3)} W₁₁^({1324})/2 12 u₁₂ = [1 −1 −1 1]^(T) W₁₂ ^({1}) W₁₂ ^({12})/{square rootover (2)} W₁₂ ^({123})/{square root over (3)} W₁₂ ^({1234})/2 13 u₁₃ =[1 −1 1 −1]^(T) W₁₃ ^({1}) W₁₃ ^({13})/{square root over (2)} W₁₃^({123})/{square root over (3)} W₁₃ ^({1324})/2 14 u₁₄ = [1 1 −1 −1]^(T)W₁₄ ^({1}) W₁₄ ^({13})/{square root over (2)} W₁₄ ^({123})/{square rootover (3)} W₁₄ ^({3214})/2 15 u₁₅ = [1 1 1 1]^(T) W₁₅ ^({1}) W₁₅^({12})/{square root over (2)} W₁₅ ^({123})/{square root over (3)} W₁₅^({1234})/2

In table 1, W_(n) ^((S)) is a matrix composed by taking the columns ofthe set {s} from W_(n)=I−2u_(n)u_(n) ^(H)/u_(n) ^(H)u_(n). Here, I is4×4 unitary matrix, and u_(n) is a vector given in table 2.

In the high level collaborative transmission, the precoding to be usedby the collaborative cells is not enough with the conventional codebookdesigned by taking notice of a single cell. That is, if the codebookdesigned for a single as shown in tables 1 and 2 is used, it isimpossible to expect the coherent combination of the channels of thecollaborative cells such that the received signal performanceenhancement is limited. Meanwhile, the received signal gain may varydepending on how to use the codebook for collaborative cells.Accordingly, there has been various codebook designs and utilizationmethods proposed to improve the received signal gain with inter-cellcooperative transmission. Also, there is a need of the method fortransmitting feedback information related to the inter-cell cooperativetransmission efficiently.

SUMMARY

By taking notice of the aforementioned problems of the prior art, it isan object of the present invention to provide a codebook-based feedbackinformation transmission/reception method and apparatus that is capableof improving the gain of the high level inter-cell cooperativetransmission with a codebook designed for such purpose.

Also, it is another object of the present invention to provide afeedback information transmission/reception method and apparatus that iscapable of supporting the use of a single cell-intended codebook and amultiple cell-intended codebook for the high level inter-cellcooperative transmission.

In accordance with an aspect of the present invention, a method fortransmitting feedback information for collaborative transmission in acellular radio communication system includes receiving collaborativecell information from a base station; determining preferredcollaborative cells among collaborative cells indicated by thecollaborative cell information; generating feedback informationincluding preferred cell indicators for discriminating between thepreferred collaborative cells and non-preferred collaborative cells,precoding matrix indicators for individual collaborative cells, phaseinformation representing phase compensation values of the preferredcollaborative cells, and channel quality indicators; and transmittingthe feedback information on one of a control channel and a data channel.

Preferably, the precoding matrix indicators indicate precoding vectorscorresponding to the preferred collaborative cells and non-preferredcollaborative cells.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the non-preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectormaximizing inter-cell interference in collaborative transmission andrestricted to be used for the non-preferred collaborative cell.

Preferably, the feedback information has a length varying according to anumber of collaborative cells or fixed regardless of the number ofcollaborative cells.

Preferably, the feedback informations are transmitted on the controlchannel in a subframe or across a plurality of subframes according tothe allocated transmission resource.

In accordance with another aspect of the present invention, a method forreceiving feedback information for collaborative transmission in acellular radio communication system includes receiving feedbackinformation including preferred cell indicators for discriminatingbetween the preferred collaborative cells and non-preferredcollaborative cells, precoding matrix indicators for individualcollaborative cells, phase information representing phase compensationvalues of the preferred collaborative cells, and channel qualityindicators, through one of a control channel and a data channel; andscheduling collaborative transmission based on the feedback information.

Preferably, the precoding matrix indicators indicate precoding vectorscorresponding to the preferred collaborative cells and non-preferredcollaborative cells.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the non-preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectormaximizing inter-cell interference in collaborative transmission andrestricted to be used for the non-preferred collaborative cell.

Preferably, the feedback information has a length varying according to anumber of collaborative cells or fixed regardless of the number ofcollaborative cells.

Preferably, the feedback informations are received on the controlchannel in a subframe or across a plurality of subframes according tothe allocated transmission resource.

In accordance with another aspect of the present invention, an apparatusfor transmitting feedback information for collaborative transmission ina cellular radio communication system includes a controller whichdetermines preferred collaborative cells among collaborative cellsindicated by the collaborative cell information and generates feedbackinformation including preferred cell indicators for discriminatingbetween the preferred collaborative cells and non-preferredcollaborative cells, precoding matrix indicators for individualcollaborative cells, phase information representing phase compensationvalues of the preferred collaborative cells, and channel qualityindicators.

Preferably, the precoding matrix indicators indicate precoding vectorscorresponding to the preferred collaborative cells and non-preferredcollaborative cells.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the non-preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectormaximizing inter-cell interference in collaborative transmission andrestricted to be used for the non-preferred collaborative cell.

Preferably, the feedback information has a length varying according to anumber of collaborative cells or fixed regardless of the number ofcollaborative cells.

Preferably, the apparatus for transmitting feedback information forcollaborative transmission further includes a control channel generatorwhich generates control channel symbols with the feedback information; adata channel generator which generates data channel symbols with thefeedback information; a multiplexer which maps the control and datachannel symbols to respective control and data channels; and atransmission processor which transmits multiplexed control and datachannels, wherein the controller includes a controller for controllingthe control channel generator, data channel generator, and multiplexerto transmit the feedback information through one of the control and datachannels.

Preferably, the controller controls the control channel generator, datachannel generator, and multiplexer to transmit all of the feedbackinformations on the control channel in one subframe or across aplurality of subframes separately.

In accordance with still another aspect of the present invention, anapparatus for receiving feedback information for collaborativetransmission in a cellular radio communication system includes a controlchannel decoder which decodes a received control channel; a data channeldecoder which decodes a received data channel; and a controller whichcontrols the control channel decoder and the data channel decoder toreceive feedback information including preferred cell indicators fordiscriminating between the preferred collaborative cells andnon-preferred collaborative cells, precoding matrix indicators forindividual collaborative cells, phase information representing phasecompensation values of the preferred collaborative cells, and channelquality indicators, through one of a control channel and a data channel.

Preferably, the precoding matrix indicators indicate precoding vectorscorresponding to the preferred collaborative cells and non-preferredcollaborative cells.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectorminimizing inter-cell interference in collaborative transmission andrecommended to be used for the non-preferred collaborative cell.

Preferably, the precoding matrix indicator indicates a precoding vectormaximizing inter-cell interference in collaborative transmission andrestricted to be used for the non-preferred collaborative cell.

Preferably, the feedback information has a length varying according to anumber of collaborative cells or fixed regardless of the number ofcollaborative cells.

Preferably, the controller controls the control channel decoder toreceive all of the feedback informations on the control channel in onesubframe or across a plurality of subframes.

The present invention provides a codebook-based compressed feedbackinformation report method and apparatus improving the gain of the highlevel inter-cell cooperative transmission with a codebook designed forsuch purpose.

Particularly, the present invention proposes compressed feedback formatsavailable for use with a single cell-intended codebook and a multiplecell-intended codebook and method and apparatus fortransmitting/receiving the compressed feedback formats so as to managethe high level inter-cell cooperative transmission system efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of an uplink subframe basedon Single-Carrier Frequency Division Multiple Access in an LTE system.

FIGS. 2 and 3 are diagrams illustrating feedback information accordingto the first embodiment of the present invention.

FIGS. 4 and 5 are a flowchart illustrating the feedback informationtransmission method according to the first embodiment of the presentinvention.

FIG. 6 is a flowchart illustrating the feedback information receptionmethod according to the first embodiment of the present invention.

FIGS. 7 and 8 are diagrams illustrating feedback informations accordingto the second embodiment of the present invention.

FIGS. 9 and 10 are diagrams illustrating feedback informations accordingto the third embodiment of the present invention.

FIGS. 11 and 12 are diagrams illustrating feedback information accordingto the fourth embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of thetransmission apparatus for transmitting the feedback informationaccording to an embodiment of the present invention.

FIG. 14 is a block diagram illustrating the reception apparatus forreceiving the feedback information according to an embodiment of thepresent invention.

FIG. 15 is a flowchart illustrating the feedback informationtransmission method according to an embodiment of the present invention.

FIG. 16 is a flowchart illustrating the feedback information receptionmethod according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. Detailed description of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the present invention. Further, the terms used herein are defined inconsideration of the functions in the present invention, and can bechanged depending on the intentions of users, or precedents. Therefore,the definition of the following terms must be understood based on theentire content of the specification of the present invention.

Although the description is directed to an OFDM-based radiocommunication system, especially 3GPP EUTRA standard, in the followingembodiments of the present invention, the subject matter of the presentinvention can be applied to other types of communication systems havingthe similar technical background and channel format with minormodification without departing from the scope of the present invention,and this is obvious to those skilled in the art of the presentinvention.

A description is made of the codebook-based feedback information reporttransmission/reception method and apparatus for high level inter-cellcooperative transmission in a cellular radio communication systemaccording to an embodiment of the present invention.

In all of the embodiments, the collaborative cells can be determined inview of the network or the terminal. In case that the collaborativecells are determined in view of the network, the inter-cell cooperationis limited due to the restriction of the physical backhaul between basestations such that all of the terminals located in a certain cell havethe same collaborative cells, while the collaborative cellsdetermination in view of the terminal enables the base station todetermine the collaborative cells per terminal on the basis of thereceived signal powers and Signal to Interference plus Noise Ratios ofthe neighbor cells that are measured and reported by the terminal.

According to an embodiment of the present invention, the terminaltransmits the information necessary for the high level inter-cellcooperative transmission to the base station. The information necessaryfor the inter-cell cooperative transmission is referred to as “feedbackinformation” of which format can be changed according to the codebookproposed in the present invention. Descriptions are made of theembodiments of the present invention.

First Embodiment

FIGS. 2 and 3 are diagrams illustrating feedback information accordingto the first embodiment of the present invention.

The feedback information depicted in FIGS. 2 and 3 are defined for useof the codebook designed for a single cell. The codebook designed forsingle cell has been described with reference to tables 1 and 2.

It is assumed that a collaborative cell configuration method in whichmultiple cells (base stations) involve the transmission is used and thebase station determines the collaborative cells for the terminal andnotifies the terminal of the determination result such that the terminalknows the number of collaborative cells and identifies the cells.According to the first embodiment of the present invention, it isassumed that the number of collaborative cells is 3.

Referring to FIGS. 2 and 3, the feedback information according to thefirst embodiment includes a Preferred Cell Indicator 201 and 221, a RankIndicator (RI) 202 and 222, a Precoding Matrix Indicator (PMI) 203 and223, a Phase Information 204 and 224, and a Channel Quality Indicator(CQI) 205 and 225.

The Preferred Cell Indicator 201 and 221 indicates the preferred celland the non-preferred cell using a bitmap among the collaborative cells.Assuming three collaborative cells, if indicator bit is set to 1 for thepreferred cell and 0 for the non-preferred cell.

RI 202 and 222 indicates a number of Ranks to be used by thecollaborative base stations which is determined depending on the channelstate.

PMI 203 and 223 includes the codebook index information indicating aprecoding vector required or restricted in use for the individualcollaborative cells. PMI 203 and 223 includes PMIs 206, 207, 208, 226,227, and 228 mapped to the respective collaborative cells. the precodingvectors denoted by reference numbers 211, 213, 231, and 233 indicatesPMI (PMI1, PMI3) mapped to the preferred cells, and reference number 212and 232 denotes PMI (PMI2) mapped to non-preferred cells.

Here, the PMIs 206, 208, 226, and 226 mapped to the preferredcollaborative cells 211, 213, 231, and 233 include values requesting thepreferred collaborative cells 211, 213, 231, and 233 for use ofprecoding vectors mapped to the PMI. Meanwhile, the PMIs 203 and 227mapped to the non-preferred cells include the precoding vector valuesthat are recommended to be used by the non-preferred collaborative cellsdue to the low interference probability. Also, the PMIs 203 and 227mapped to the non-preferred collaborative cells can include theprecoding vectors that are recommended to be not used by thenon-preferred collaborative cells due to the high interferenceprobability.

Referring to FIGS. 2 and 3, the terminal indicates the preferredcollaborative cells in the form of bitmap as denoted by reference number201 and 221 and selects the RI 202 and 222 and PMI 206, 208, 226, and228 preferred for the indicated cells. Here, it is assumed that thepreferred cell indicator is set to 1 while the non-preferred cellindicator is set to 0. Also, it is assumed that the same RI 202 and 222is used for the preferred collaborative cells. PMI 206, 207, 208, 226,and 228 means the index in the codebook designed for single cell.

PI 204 and 224 is the information on the compensation value forcompensating channel phase between the preferred cells for collaborativetransmission when using the codebook designed for signal cell. In caseof using the codebook designed for single cell, phase difference occursbetween the cells such that the phase of the precoding matrix is shiftedaccording to the phase difference of a cell with the reference cell(e.g. serving cell). PI 204 and 224 means the phase compensation valueof such collaborative cells.

CQI 205 and 225 is the value calculated in consideration of the channelstates of the collaborative cells in collaborative transmission and canbe obtained based on the aforementioned information including RI, PMI1,PMI2, PMI3, and PI.

According to an embodiment of the present invention, the above-describedfeedback informations can be transmitted simultaneously or separately.

In case of FIG. 2, all of the feedback informations are defined in onefeedback format and mapped to the control channel (e.g. PUCCH) of asubframe so as to be transmitted to the base station at a predeterminedinterval or mapped to the allocated data channel (e.g. PUSCH) so as tobe transmitted to the base station in response to the feedback requestof the base station.

If no feedback format for carrying all of the feedback informations isdefined and thus it is impossible to transmit the feedback informationon PUCCH of one subframe, the feedback informations can be transmittedseparately in consideration of the properties of individual feedbackinformations as shown in FIG. 3. That is, the preferred collaborativecell indicator 221, RI 222, PMI1 226, PMI2 227, PMI3 228, PI 224, andCQI 225 can be mapped in PUCCH at the PUCCH transmission interval of theterminal so as to be transmitted separately. In case that the feedbackinformations are transmitted at a subframe interval T on PUCCH as shownin FIG. 3, it takes a time duration of 7×T until receiving all of thefeedback information.

According to the above-described first embodiment of the presentinvention, the terminal transmits the PMIs of the non-preferredcollaborative cells as well the preferred collaborative cells to thebase station so as to improve the received signal gain significantly inthe collaborative transmission. According to the first embodiment of thepresent invention, the feedback information is transmitted in thetransmission format having a fixed size regardless of the number ofcollaborative cells such that it is possible to reduce the processingcomplexity of the receiver. In the first embodiment, PI 204 and 224 asthe channel phase information between cells is requested for all of thecollaborative cells with the exception of the serving cell. Accordingly,as the number of the collaborative cells having the real transmissionincreases, the PI information amount increases. Thus, it is preferred todetermine the fixed size of the feedback format in consideration of themaximum PI information amount for all of the collaborative cells. If thenumber of the preferred collaborative cells is less than maximum numberof the collaborative cells, the empty space of the PI information iszero-padded to match the fixed format size. Another method for fixingthe feedback information size is to define the format for carrying thePI information of one cell under the assumption that all of thepreferred collaborative cells using the same PI.

A description is made of the method for transmitting/receiving feedbackinformation according to an embodiment of the present inventionhereinafter.

The feedback information transmission method according to the firstembodiment of the present invention is described first hereinafter.FIGS. 4 and 5 are a flowchart illustrating the feedback informationtransmission method according to the first embodiment of the presentinvention.

Although not depicted in FIGS. 4 and 5, the terminal receives theinformations on the collaborative cells such as cell identifiers (IDs)from the base station, and it is assumed that both the base station andterminal know the collaborative cells and a number of the collaborativecells.

Referring to FIGS. 4 and 5, the terminal acquires PUCCH transmissioninterval for reporting feedback information (301).

The terminal determines preferred collaborative cells for which feedbackinformations are generated (302). That is, the terminal generatespreferred cell indicators 201 and 221 indicating the preferredcollaborative cells and the non-preferred collaborative cells in theform of a bitmap. As aforementioned, the indicator is set to 1 for thepreferred collaborative cell and 0 for the non-preferred collaborativecell.

After determining the preferred collaborative cells and thenon-preferred collaborative cells, the terminal generates the feedbackinformations (RI, PMI, PI, and CQI) on the preferred and non-preferredcollaborative cells (303). That is, the terminal selects PMI for eachpreferred collaborative cell and PMI for each non-preferredcollaborative cell. Here, the terminal can select PMI recommended to beused for the preferred collaborative cells and PMI recommended to be notused for the non-preferred collaborative cells. The terminal also selectRI to be used in common for the cell and PI of the neighbor cells aroundthe serving cell. The terminal generates CQI in consideration of all ofPMI, RI, and PI of the cells involved in the collaborative transmission.

In this way, the terminal generates the feedback informations throughsteps 301 and 303.

Once the feedback information are generated, the terminal determineswhether to transmit the feedback information on PUSCH or PUCCH (304).The determination is made depending on the resource allocation state.

If the base station has allocated PUSCH for feedback information reportfor the collaborative transmission, the terminal performs channel codingand mapping on the generated feedback informations on the PUSCH resourceallocated for the feedback information report and (305). Next, theterminal multiplexes PUSCH and RS and transmits output signal (305).

Otherwise if the base station has not allocated PUSCH for feedbackinformation report, the terminal determines whether the generatedfeedback informations can be transmitted on PUSCH in one subframe (307).

If there is a feedback format for PUCCH that can carry all of thefeedback informations, the terminal performs channel coding on thefeedback informations at feedback information report interval informedby the base station, maps the coded information to PUCCH, multiplexesPUSCH and RS, and transmits the multiplexed signal.

If it is impossible to transmit all of the feedback informations onPUSCH in one subframe, the terminal performs channel coding on therespective informations 221, 222, 226, 227, 228, 224, and 225 separatelyin consideration of their properties as shown in FIG. 3 (309). Next, theterminal maps the channel-coded feedback informations to PUCCH at thefeedback information report interval informed by the base station totransmit in sequence.

As described above, according to an embodiment of the present invention,it is possible to transmit the feedback information on one of PUCCH andPUSCH, and in case of using PUCCH, the feedback information can betransmitted in one subframe or multiple subframes separately.

The feedback information reception method according to the firstembodiment of the present invention is described hereinafter. FIG. 6 isa flowchart illustrating the feedback information reception methodaccording to the first embodiment of the present invention.

Referring to FIG. 6, the base station demultiplexes the receivedsubframe into PUCCH, PUSCH, and RS (401).

The base station determines whether the subframe includes PUSCHallocated for feedback information report on the collaborative cells fora certain terminal (402). As aforementioned, the terminal transmits thefeedback information on one of PUSCH and PUCCH, such that the basestation determines whether the feedback information is received on whichof PUSCH and PUCCH.

If there is PUSCH allocated for the feedback information at step 402,the base station de-maps the symbol carrying the feedback informationfrom PUSCH region (403). Next, the base station performs decoding thesymbol of the de-mapped feedback information to acquire the feedbackinformation transmitted by the terminal and then uses the downlinkscheduling information (404).

Otherwise if there is no PUSCH allocated for the feedback information atstep 402, the base station de-maps the feedback information symbol fromthe PUSCH region at the feedback information report interval of thecorresponding terminal (405).

Next, the base station performs decoding on the de-mapped feedbackinformation symbol to acquire the feedback information on thecorresponding terminal (406).

If the feedback informations are received separately, the base stationreceives all of the feedback information and then uses the feedbackinformation for downlink scheduling (407).

Second Embodiment

A description is made of the feedback information according to thesecond embodiment of the present invention. FIGS. 7 and 8 are diagramsillustrating feedback informations according to the second embodiment ofthe present invention.

The feedback information formats shown in FIGS. 7 and 8 are defined forthe case where the codebook designed for multiple cells (hereinafter,referred to as multi-cell codebook).

The multi-cell codebook is a codebook generated for multiple cells andcan be designed in such a manner of combining the single cell codebooksshown in tables 1 and 2 and the quantized PI. Such a multi-cell codebookincludes only the precoding vector for the preferred collaborative cellssuch that its size can change according to the number of the preferredcollaborative cells. This means that the sizes of the feedbackinformation formats proposed in FIGS. 7 and 8 vary according to thenumber of the preferred collaborative cells. As aforementioned in thefirst embodiment, it is assumed that the base station and terminal knowthe collaborative cells and the number of collaborative cells. Althoughthe description is directed to the case where the number ofcollaborative cells is 3, the present invention is not limited thereto.

Referring to FIGS. 7 and 8, the feedback information according to thesecond embodiment of the present invention includes Preferred CellIndicator 501 and 521, Rank Indicator (RI) 502, Multi-cell PrecodingMatrix Indicator (Multi-cell PMI) 503 and 523, and Channel QualityIndicator (CQI) 504 and 524.

The Preferred Cell Indicator 501 and 521 indicates the preferred cell ornon-preferred cell of the terminal among the collaborative cells in theform of a bitmap.

RI 502 and 522 indicates a number of Ranks to be used commonly by thecollaborative cells and determined according to the channel state.

Multi-cell PMI 503 and 523 is basically to recommend the precodingvectors for the preferred cells indicated by the preferred cellindicator 501 and 521, and includes only the precoding vectors for thepreferred cells unlike the first embodiments. The multi-cell codebookfurther includes the compensation values determined in consideration ofthe phases of the collaborative cells in the multi-cell environment.Accordingly, the multi-cell PMI 503 and 523 denotes the precoding vectorvalues mapped to the collaborative cells preferred by the serving cellin the multi-cell codebook determined in consideration of the phasecompensation values.

The terminal indicates the preferred cells among the collaborative cellsin the form of a bitmap. The terminal also selects the RI 502 and 522and multi-cell PMI 503 and 523 for the each indicated cell. Here, it isassumed that the preferred collaborative cell is indicated by 1, and thenon-preferred collaborative cell is indicated by 0. Also, it is assumedthat the same RI is used for all of the collaborative cells. Themulti-cell PMI denotes the index in the multi-cell codebook designed formultiple cells, and the multi-cell codebook is designed to include theinter-cell phase information.

CQI 504 and 524 is the value determined in consideration of channelstates of the collaborative cells in collaborative transmission, and theterminal determines CQI 504 and 524 that can be acquired based on theselected information (RI and multi-cell PMI).

According to an embodiment of the present invention, the above-describedfeedback informations can be transmitted at a time or separately.

That is, the feedback informations can be defined into a feedback formatto be mapped to PUCCH in a subframe and transmitted to the base stationat a certain interval or the resource allocated in PUSCH in response tothe feedback information request from the base station.

If there is no feedback format defined for carrying all of the feedbackinformations and thus if it is impossible to map the feedbackinformations to PUCCH of one subframe, the feedback informations can betransmitted separately in consideration of their properties as shown inFIG. 8. That is, the Preferred Cell Indicator 521, RI 522, PMI 523, andCQI 524 can be transmitted separately as mapped to PUCCH at PUCCHtransmission interval of the terminal. In case that the feedbackinformations are transmitted separately on PUCCH at an interval of Tsubframes as shown in FIG. 8, the base station has to receive 4×Tsubframes to acquire all of the feedback informations. In case that thefeedback informations are transmitted separately as shown in FIG. 8, thebase station decodes the preferred cell indicator received first toacquire the information on the number of the preferred collaborativecells and estimate the size of the PMI information 523 for the multiplecells that is to be received afterward. Here, it is assumed that thesize of the multi-cell codebook is variable depending on the number ofthe preferred collaborative cells.

According to the second embodiment of the present invention, thefeedback information can be fixed in size. In order to use a fixedfeedback format, it is preferred to determine the size of the feedbackformat in consideration of the maximum codebook length for transmittingthe feedback informations on all of the collaborative cells and fill theempty space for PMIs with zero bits.

Third Embodiment

A description is made of the feedback informations according to thethird embodiment of the present invention. FIGS. 9 and 10 are diagramsillustrating feedback informations according to the third embodiment ofthe present invention.

The feedback formats proposed in FIGS. 9 and 10 are defined for the caseof using the codebook designed for multiple cells and can be designed inthe form of combination of a single cell codebook and the quantized PIsfor the collaborative base stations. Unlike the second embodiment,however, the multi-cell codebook proposed in the third embodiment is thesize of the codebook is fixed regardless of the number of preferredcollaborative cells. The multi-cell codebook is designed with a fixedsize regardless of the number of the collaborative cells such thatdifferent codebooks are used depending on the number of thecollaborative cells while maintaining the size of the feedback format.

As aforementioned in the first embodiment, it is assumed that the basestation and terminal know the collaborative cells and the number ofcollaborative cells, and the number of collaborative cells is limited to3 in the third embodiment too.

Referring to FIGS. 9 and 10, the feedback informations according to thethird embodiment of the present invention includes Preferred CellIndicator 601 and 621, Rank Indicator (RI) 602 and 622, Multi-cellPrecoding Matrix Indicator (Multi-cell PMI) 603 and 623, and ChannelQuality Indicator (CQI) 604 and 624.

The preferred cell indicator 601 and 621 indicates the preferred cell ornon-preferred cell of the terminal among the collaborative cells in theform of a bitmap.

RI 602 and 622 indicates a number of Ranks to be used commonly by thecollaborative cells and determined according to the channel state.

PMI 603 and 623 is basically to recommend the precoding vectors for thepreferred cells indicated by the preferred cell indicator 601 and 621.Similar to the second embodiment, the precoding vectors includes thecompensation values determined in consideration of the phases of thecollaborative cells in the multi-cell environment. However, themulti-cell codebook according to the third embodiment has a fixed sizeregardless of the number of collaborative cells. Since the feedbackinformations are transmitted in the format fixed in size regardless ofthe number of collaborative cells, it is possible to reduce theprocessing complexity of the receiver.

The terminal indicates the preferred cells among the collaborative cellsin the form of a bitmap. The terminal also selects the RI 602 and 622and multi-cell PMI 603 and 623 for the each indicated cell. Here, it isassumed that the preferred collaborative cell is indicated by 1, and thenon-preferred collaborative cell is indicated by 0; and the same RI isused for all of the collaborative cells. The PMI denotes the index inthe multi-cell codebook designed for multiple cells, and the multi-cellcodebook is designed to include the inter-cell phase information.

CQI 604 and 624 is the value determined in consideration of channelstates of the collaborative cells in collaborative transmission, and theterminal determines CQI 604 and 624 that can be acquired based on theselected information (RI and PMI).

According to an embodiment of the present invention, the above-describedfeedback informations can be transmitted at a time or separately.

That is, the feedback informations can be defined into a feedback formatto be mapped to PUCCH in a subframe and transmitted to the base stationat a certain interval or the resource allocated in PUSCH in response tothe feedback information request from the base station.

If there is no feedback format defined for carrying all of the feedbackinformations and thus if it is impossible to map the feedbackinformations to PUCCH of one subframe, the feedback informations can betransmitted separately in consideration of their properties as shown inFIG. 10. That is, the Preferred Cell Indicator 621, RI 622, PMI 623, andCQI 624 can be transmitted separately as mapped to PUCCH at PUCCHtransmission interval of the terminal. In case that the feedbackinformations are transmitted separately on PUCCH at an interval of Tsubframes as shown in FIG. 10, the base station has to receive 4×Tsubframes to acquire all of the feedback informations.

Fourth Embodiment

A description is made of the feedback informations according to thefourth embodiment of the present invention. FIGS. 11 and 12 are diagramsillustrating feedback information according to the fourth embodiment ofthe present invention.

The feedback formats proposed in FIGS. 11 and 12 are defined for thecase of using the codebook designed for multiple cells.

The multi-cell codebook considered in the fourth embodiment of thepresent invention can be designed to include all available combinationsof the collaborative cells and phase informations of the respectivecombinations, and the codebook according to the fourth embodiment isreferred to as “global codebook.”

The global codebook includes all of the preferred cells and precodingvectors of the preferred cells and phase compensation values of thepreferred cells. That is, the PMI information selected from the globalcodebook includes the information on the preferred collaborative cells,PMIs of the respective cells, and RI information. Such a global codebookcan be built by combining the codebooks described in the second andthird embodiments for all available collaborative cells.

Referring to FIGS. 11 and 12, the feedback informations according to thefourth embodiment of the present invention includes Rank (RI) 701 and721, Precoding Matrix Indicator (PMI) 702 and 722, and Channel QualityIndicator (CQI) 702 and 723.

RI 702 and 722 indicates a number of Ranks to be used commonly by thecollaborative cells and determined according to the channel state.

PMI 703 and 723 is basically to recommend the precoding vectors for thepreferred cells. However, the PMI 702 and 722 according to the fourthembodiment indicates the preferred cells, precoding vectors of thepreferred cells, and phase compensation values of the respectivecollaborative cells.

CQI 703 and 723 is the value determined in consideration of channelstates of the collaborative cells in collaborative transmission, and theterminal selects preferred RI 701 and 721 and PMI 702 and 722 andcalculates CQI 703 and 723 based on the selected RI and PMI information.

According to an embodiment of the present invention, the above-describedfeedback informations can be transmitted at a time or separately.

As shown in FIG. 11, the feedback informations can be defined into afeedback format to be mapped to PUCCH in a subframe and transmitted tothe base station at a certain interval or the resource allocated inPUSCH in response to the feedback information request from the basestation.

If there is no feedback format defined for carrying all of the feedbackinformations and thus if it is impossible to map the feedbackinformations to PUCCH of one subframe, the feedback informations can betransmitted separately in consideration of their properties as shown inFIG. 12. That is, the RI 721, PMI 722, and CQI 723 can be transmittedindependently as mapped to PUCCH at PUCCH transmission interval of theterminal. In case that the feedback informations are transmittedindependently on PUCCH at an interval of T subframes as shown in FIG.12, the base station has to receive 3×T subframes to acquire all of thefeedback informations. In the fourth embodiment, since the globalcodebook is used, the feedback format is fixed in size.

The transmission/reception apparatus according to an embodiment of thepresent invention is described hereinafter.

First of all, a description is made of a transmission apparatus fortransmitting feedback informations according to an embodiment of thepresent invention. FIG. 13 is a block diagram illustrating aconfiguration of the transmission apparatus for transmitting thefeedback information according to an embodiment of the presentinvention.

Referring to FIG. 13, the transmitter according to an embodiment of thepresent invention includes a controller 801, an RS generator 802, aPUCCH generator 803, a PUSCH generator 804, a multiplexer 805, and a TXprocessor 806. The transmitter can be implemented as a part of aterminal.

The RS generator 802, the PUCCH generator 803, and the PUSCH generator804 generate RS symbols, control channel symbols, and data channelsymbols respectively under the control of the controller 801.

The controller 801 generates feedback information which can be formattedas described in one of the first to fourth embodiments.

The controller 801 controls the RS generator 802, the PUCCH generator803, and the PUSCH generator 804 to generate RS symbols, control channelsymbols, and data channel symbols, respectively. The generated RSsymbols, control channel symbols, and data channel symbols aremultiplexed with RS symbols generated by the RS generator 802 by meansof the multiplexer 805.

At this time, the controller 801 does not allow simultaneous mapping toPUCCH and PUSCH to maintain the single carrier characteristic. In casethat the base station has allocated PUSCH resource for feedbackinformation report, the symbols of the feedback information generated bythe PUCCH generator 803 are mapped in PUSCH region and multiplexed withthe RS symbols so as to be transmitted by means of the TX processor 806.This process is performed under the control of the controller 801. If itis required to transmit the feedback information separately on PUCCH,the controller 801 controls the PUCCH generator 803 to supply theseparated feedback information symbols at an interval acquired from thebase station.

That is, the controller 801 generates feedback information and controlsto generate symbols corresponding channel according to the resourceallocated by the base station and map the symbols to the transmissionresource of the corresponding channel.

For example, in case that the resource for transmitting the feedbackinformation is allocated in PUCCH, the controller 801 controls the PUCCHgenerator 803 to generate control channel symbols carrying the feedbackinformation and controls the multiplexer 805 to map the control channelsymbols to the resource allocated in PUCCH.

In case that the resource for transmitting the feedback information isallocated in PUSCH, the controller 801 controls the PUSCH generator 804to generated data symbols carrying the feedback information and controlsthe multiplexer 805 to map the data channel symbols to the resourceallocated in PUSCH.

A description is made of the reception apparatus for receiving thefeedback information according to an embodiment of the presentinvention. FIG. 14 is a block diagram illustrating the receptionapparatus for receiving the feedback information according to anembodiment of the present invention.

Referring to FIG. 14, the reception apparatus for receiving the feedbackinformation according to an embodiment of the present invention includesa demultiplexer 901, a PUCCH decoder 902, a PUSCH decoder 903, a channelestimator 904, a controller 905, a scheduler 906, a storage 907, and areception processor 908. The reception can be a part of the basestation.

The received signal is converted into a baseband signal by the receptionprocessor 908.

The demultiplexer 901 demultiplexes the baseband signal into RS, PUCCH,and PUSCH. Here, the PUCCH and PUSCH signals are input to the PUCCHdecoder 902 and the PUSCH decoder 903 respectively, and the RS signal isinput to the channel estimator 904.

The channel estimator 904 estimates channel using RS. The channelestimation value output by the channel estimator 904 is input to thePUCCH decoder 902 and the PUSCH decoder 903 for decoding PUCCH and PUSCHsignals.

If the scheduler 906 notifies the controller 905 of the PUCCH regionallocated for the feedback information report of a certain terminal, thecontroller 905 controls to transfer the feedback information signalmapped in the PUCCH region from the demultiplexer 901 to the PUCCHdecoder 902 so as to decode the feedback information.

If the scheduler 906 notifies the controller 905 of the PUSCH regionallocated for the feedback information report of a certain terminal, thecontroller 905 controls to transfer the feedback information signalmapped in the PUSCH region from the demultiplexer 901 to the PUSCHdecoder 903 so as to decode the feedback information.

The feedback information decoded from the feedback information signal isinput to the controller 905, and the controller forwards the feedbackinformation to the scheduler 906.

The controller 905 can recognize that the feedback informations of acertain terminal are received separated at a given interval based on theinformation provided by the PUCCH decoder 902.

The controller 905 controls to the feedback informations receivedseparately in the storage 907 until the entire feedback information of acertain terminal are received completely. Once the feedback informationsof a certain terminal are received completely, the controller 905transfers the complete feedback information stored in the storage to thescheduler 906.

That is, the scheduler 906 notifies the controller 905 of which channelis used to carry the feedback information such that the controller 905receives the feedback information through the corresponding decoder. Ifthe feedback informations are received on PUCCH in a plurality ofsubframes, the controller 905 accumulates the feedback informations inthe storage 907 until all of the feedback informations are receivedcompletely.

The feedback information transmission/reception method according to anembodiment of the present invention is described hereinafter.

First of all, a description is made of the feedback informationtransmission method according to an embodiment of the present invention.FIG. 15 is a flowchart illustrating the feedback informationtransmission method according to an embodiment of the present invention.

Although not depicted in FIG. 15, the terminal receives the informationson the collaborative cells such as collaborative cell identifier (ID)from the base station in prior such that both the base station andterminal know the collaborative cells and the number of collaborativecells.

Referring to FIG. 15, the terminal is allocated the resource fortransmitting the feedback information (1001). The terminal can beallocated the transmission resource through PDCCH, and the resource fortransmitting the feedback information can be allocated in one of PUCCHand PUSCH. Particularly in case that the resource is allocated in PUCCH,the feedback informations can be transmitted at a time in one subframeor separately in a plurality of subframes.

Next, the terminal generates feedback information (1003). The feedbackinformations can be formatted as proposed in one of the first to fourthembodiments.

Once the feedback information is generated, the terminal determines theresource for transmitting the feedback information (1005). The feedbackinformation transmission is performed on the transmission resourceallocated by the base station.

In case that the feedback information transmission resource is allocatedin PUSCH, the terminal transmits the feedback information through PUSCH(1007).

In case that the feedback information transmission resource is allocatedin PUCCH, the terminal determines whether to transmit the feedbackinformations at a time in one subframe (1009). That is, the base stationdetermines whether it is possible to transmit all of the feedbackinformations allocated the PUCCH resource in a subframe.

If it is possible to transmit the feedback information in a subframe,the terminal transmits all of the feedback informations on PUCCH in onesubframe as described with reference to FIGS. 2, 7, 9, and 11 (1011).

If it is impossible to transmit the feedback information in a subframe,the terminal transmits the feedback informations separately on PUCCHacross a plurality of subframes as described with reference to FIGS. 3,8, 10, and 12 (1013).

According to an embodiment of the present invention, the feedbackinformation can be transmitted on one of PUCCH and PUSCH. Particularlyin case of using PUCCH, the feedback information can be transmitted inone subframe or across a plurality subframes according to the allocatedtransmission resource.

A description is made of the method for receiving the feedbackinformation transmitted as above. FIG. 16 is a flowchart illustratingthe feedback information reception method according to an embodiment ofthe present invention.

Referring to FIG. 16, if a signal transmitted by a terminal is received,the base station demultiplexes the received subframe into PUCCH, PUSCH,and RS (1101).

Next, the base station determines which channel is used to transmit thefeedback information (1003). That is, the base station determineswhether the feedback information is transmitted on PUSCH or PUCCH. Thedetermination is made based on the information on the transmissionresource allocated to the terminal.

If the feedback information is transmitted on PUSCH, the base stationreceives the feedback information on the resource allocated in PUSCH(1105).

Otherwise if the feedback information is transmitted on PUCCH, the basestation determines whether all of the feedback informations are receivedin a subframe (1007). That is, the base station determines whether theresource allocated on PUCCH in a subframe for the feedback informationhas a size enough to carry all of the feedback informations.

If the size of the resource allocated on PUCCH in a subframe has thesize enough to accommodate all of the feedback informations, the basestation receives all of the feedback informations on PUCCH in onesubframe as described with reference to FIGS. 2, 7, 9, and 11 (1109).

Otherwise if the size of the resource allocated on PUCCH in a subframehas a size not enough to accommodate all of the feedback informations,the base station receives the feedback informations on PUCCH across aplurality of subframes as described with reference to FIGS. 3, 8, 10,and 12 (1111).

As described above, upon receipt of the feedback information through oneof PUCCH and PUSCH, the base station performs scheduling based on thefeedback information (1113). For this purpose, the base station sharethe feedback information with collaborative cells (base stations). Thecollaborative cells sharing the feedback informations perform schedulingbased on the feedback information and can execute COMP.

Although the description has been made with reference to particularembodiments, the present invention can be implemented with variousmodification without departing from the scope of the present invention.Thus, the present invention is not limited to the particular embodimentsdisclosed but will include the following claims and their equivalents.

What is claimed is:
 1. A method for transmitting feedback informationfor collaborative transmission in a cellular radio communication system,the method comprising: receiving, from a base station, collaborativecell information indicating at least three collaborative cells;determining at least two preferred collaborative cells among the atleast three collaborative cells; generating feedback informationincluding cell indicators for discriminating between the at least twopreferred collaborative cells and at least one non-preferredcollaborative cell, precoding matrix indicators for the at least twopreferred collaborative cells, and channel quality indicators; andtransmitting the feedback information via one of a control channel and adata channel, wherein the feedback information is transmitted in atransmission format having a fixed size regardless of a number ofcollaborative cells.
 2. The method of claim 1, wherein the precodingmatrix indicators indicate precoding vectors corresponding to the atleast two preferred collaborative cells.
 3. The method of claim 1,wherein the precoding matrix indicators indicate a precoding vector,minimizing inter-cell interference in the collaborative transmission,that is recommended to be used for the at least two preferredcollaborative cells.
 4. The method of claim 1, wherein the precodingmatrix indicators indicate a precoding vector mapped to the at least twopreferred collaborative cells in a multi-cell codebook that is a singlecodebook generated for the at least three collaborative cells.
 5. Themethod of claim 4, wherein the multi-cell codebook includes compensationvalues determined based on phases of the at least three collaborativecells.
 6. A method for receiving feedback information for collaborativetransmission in a cellular radio communication system, the methodcomprising: receiving feedback information including cell indicators fordiscriminating between at least two preferred collaborative cells and atleast one non-preferred collaborative cell, precoding matrix indicatorsfor the at least two preferred collaborative cells, and channel qualityindicators, via one of a control channel and a data channel; andscheduling the collaborative transmission based on the feedbackinformation, wherein the feedback information is transmitted in atransmission format having a fixed size regardless of a number ofcollaborative cells.
 7. The method of claim 6, wherein the precodingmatrix indicators indicate precoding vectors corresponding to the atleast two preferred collaborative cells.
 8. The method of claim 6,wherein the precoding matrix indicators indicate a precoding vector,minimizing inter-cell interference in the collaborative transmission,that is recommended to be used for the at least two preferredcollaborative cells.
 9. The method of claim 6, wherein the precodingmatrix indicators indicate a precoding vector mapped to the at least twopreferred collaborative cells in a multi-cell codebook that is a singlecodebook generated for at least three collaborative cells.
 10. Themethod of claim 9, wherein the multi-cell codebook includes compensationvalues determined based on phases of the at least three collaborativecells.
 11. An apparatus for transmitting feedback information forcollaborative transmission in a cellular radio communication system, theapparatus comprising: a receiver configured to receive a first RadioFrequency (RF) signal; a transmitter configured to transmit a second RFsignal; and a controller configured to: control the receiver to receive,from a base station, the first RF signal including collaborative cellinformation indicating at least three collaborative cells, determine atleast two preferred collaborative cells among the at least threecollaborative cells, generate feedback information including cellindicators for discriminating between the at least two preferredcollaborative cells and at least one non-preferred collaborative cell,precoding matrix indicators for the at least two preferred collaborativecells, and channel quality indicators, and control the transceiver totransmit the second RF signal including the feedback information via oneof a control channel and a data channel, wherein the feedbackinformation is transmitted in a transmission format having a fixed sizeregardless of a number of collaborative cells.
 12. The apparatus ofclaim 11, wherein the precoding matrix indicators indicate precodingvectors corresponding to the at least two preferred collaborative cells.13. The apparatus of claim 11, wherein the precoding matrix indicatorsindicate a precoding vector, minimizing inter-cell interference in thecollaborative transmission, that is recommended to be used for the atleast two preferred collaborative cells.
 14. The apparatus of claim 11,wherein the precoding matrix indicators indicate a precoding vectormapped to the at least two preferred collaborative cells in a multi-cellcodebook that is a single codebook generated for the at least threecollaborative cells.
 15. The apparatus of claim 14, wherein themulti-cell codebook includes compensation values determined based onphases of the at least three collaborative cells.
 16. An apparatus forreceiving feedback information for collaborative transmission in acellular radio communication system, the apparatus comprising: areceiver configured to receive a Radio Frequency (RF) signal; and acontroller configured to: control the receiver to receive the RF signalincluding feedback information including cell indicators fordiscriminating between at least two preferred collaborative cells and atleast one non-preferred collaborative cell, precoding matrix indicatorsfor the at least two preferred collaborative cells, and channel qualityindicators, via one of a control channel and a data channel, andschedule the collaborative transmission based on the feedbackinformation, wherein the feedback information is transmitted in atransmission format having a fixed size regardless of a number ofcollaborative cells.
 17. The apparatus of claim 16, wherein theprecoding matrix indicators indicate precoding vectors corresponding tothe at least two preferred collaborative cells.
 18. The apparatus ofclaim 17, wherein the precoding matrix indicators indicate a precodingvector, minimizing inter-cell interference in the collaborativetransmission, that is recommended to be used for the at least twopreferred collaborative cells.
 19. The apparatus of claim 17, whereinthe precoding matrix indicators indicate a precoding vector mapped tothe at least two preferred collaborative cells in a multi-cell codebookthat is a single codebook generated for at least three collaborativecells.
 20. The apparatus of claim 19, wherein the multi-cell codebookincludes compensation values determined based on phases of the at leastthree collaborative cells.